For many years, aircraft have included a backup power source as standard equipment for use in times of power outage in the main power system. This standard equipment usually is in the form of an air-driven turbine or fan which has a normal stowed position within the fuselage of the aircraft and which can be moved, usually lowered, to a deployed position in the airstream, thereby making use of the relative speed of the aircraft through the ambient air to cause the turbine blades or propellers to rotate. The rotation imparted to the blades due to their movement through the air then is used to drive an electrical generating gear system, a hydraulic pump to provide hydraulic power to the aircraft hydraulic system, or the like, during the aforementioned times of power outages. These air driven turbine arrangements often also include governor mechanisms that attempt to control the output rotational speed delivered from the propellers to electrical or hydraulic units.
In the past, a single ram air turbine was employed on a single aircraft, with that ram air turbine operatively associated with a given accessory. If the aircraft need for power was primarily hydraulic, with a small amount of electrical power required, the ram air turbine would be used to drive a pump, and aircraft batteries, or a controlled speed electrical motor driven by the ram air turbine hydraulic pump, used to provide the emergency electrical power requirements. If the primary power requirement was electrical, the ram air turbine would generally drive a generator with the small amount of hydraulic power required supplied by either accumulators or an A.C. motor driven hydraulic pump. However, in commercial and military applications today, more and more electronics are designed in the aircraft, such as in fly-by-wire flight controls. This additional electrical load, and subsequently the more even split between emergency electrical and emergency hydraulic power requirements has resulted in the need to efficiently provide both electrical and hydraulic power by driving both a generator and a pump from the ram air turbine. In addition to the need for an efficient source of long term electrical or hydraulic power is the need for extended range overwater operation of twin engine aircraft. Where, in the past, a ram air turbine was primarily intended for flight control to effect a controlled crash when all engines were inoperative, it now is desirable to use ram air turbines to provide long term electrical power to continue a flight when the aircraft engines are operating but the main aircraft generators have failed, or alternatively to provide long term hydraulic power when the main aircraft pumps have failed.
In view of these changing technologies, attempts have been made simply to add more and more accessories to the ram air turbine. For instance, this may be accomplished by adding accessories seriatum along an axial shaft. This necessitates driving all the accessories at the same rotational speed as the turbine and causes size problems in an environment where compact lightweight envelope design is desired. In addition, coupling systems must be run from the deployed pump and generator into the aircraft fuselage, using "soft" piping or a rotary joint which cause reliability problems. Whether it be in the form of additional gearboxes, piping, extended shafts or the like, deployment of extraneous components in the airstream causes obvious problems.
This invention is directed to a new and improved drive system between a ram air turbine and a plurality of accessory power units of the character described and which are located directly in the aircraft fuselage to satisfy the needs and solve the problems outlined above.